When Leanne Weinshenker came home after her first year at Northwestern University, she was aghast when she couldn’t zip up the dress she kept for formal family gatherings.

“I was aware that I’d put on some weight, but I had no idea how much until I went to put on a dress I’d worn multiple times, and it was nowhere close to getting zipped up,” she said.

“For me, it was the combination of being in school at a time when big, baggy clothes were in, and going months without really seeing myself naked. And waiting in line at the dining hall: ‘Oh, look! Fresh dinner rolls!’ ‘Oh, they just put out some fresh cookies! I’ll snack on those while I’m waiting in line.’ I was eating without realizing that I’d eaten more than I normally would. For me, the ‘Freshman 15’ was more like the Freshman 20 or 25.”

The Freshman 15 — the added weight that an average 18-year-old packs on within a few months of leaving the family home for a college dorm or first apartment — might be a trope, but it’s also a real risk.

“It’s something that quietly happens, a subtle change in lifestyle, when kids who play on a team or have structured exercise in high school suddenly don’t have daily exercise as part of their lives,” said Children’s Hospital adolescent medicine physician Amy Sass.

“The Freshman 15, if it happens, happens pretty quickly, within that first semester. The kids might not really be aware of it until they go home for Thanksgiving or winter break, and people say, ‘Wow! What happened?'”

Alcohol alone can contribute most of the dreaded Freshman 15. Yes, underage drinking is illegal, but it’s pervasive on and off campus. Often young adults don’t realize how many calories are in the drinks they’re throwing back.

“Alcohol is high in empty calories, and for many students, drinking is something they’re definitely engaging in, especially binge drinking,” Sass said.

“I’m not sure if students do the math for how many calories are in a beer, or how much alcohol it takes to get dangerously intoxicated. Kids get some nutrition information in high school, but it’s mixed in with everything else. When they leave home, there’s stress, social eating, and suddenly nobody is monitoring them the way their parents used to. “

A University of Illinois at Chicago study found that when young adults eat fast food, they consume an extra 309 calories between deep-fried food, high-sugar drinks and side orders. That’s not a problem for a high school student who plays in a soccer league or runs for the cross-country team. But it becomes a problem for a college student who doesn’t make the cut for the university sports teams.

“Exercise, for the majority of kids, decreases with that transition to campus life,” Sass said.

“Some of it is a lack of awareness. Some kids don’t know where the gym is. And for community college students, there may not be a school gym, and they may be intimidated by the joining fee and monthly fees of commercial fitness centers, especially if they’re on a budget.”

But, as Sass noted, walking around campus counts as exercise. So does joining an intramural team or the school outdoor club, which can lead to an interest in hiking and other activities that continues well past college.

And then there’s nutrition.

“It’s all about seeking balance,” Sass says.

“Is it OK to eat pizza with friends at 2 a.m.? Yes. Should you do that every night? No. Be mindful of how you’re sweetening your coffee. Do you know that there are 300 calories in a 20-ounce vanilla soy latte? It’s about nutrition, but it’s also about regular physical exercise, getting enough sleep, being mindful about a consistent bedtime, and turning off your cellphone and your computer when you’re supposed to be sleeping.”

Florida’s state social services agency investigated Nikolas Cruz’s home life more than a year before police say he killed 17 people at his former high school, closing the inquiry after determining that his “final level of risk is low,” despite learning that the teenager had behavioral struggles and was planning to buy a gun, according to an investigative report.